The purpose of this contract is to test the immunogenicity and efficacy of a new pertussis vaccine (pertussis toxin inactivated with hydrogen peroxide) developed by the Laboratory of Developmental and Molecular Immunity (LDMI), Intramural Research Program, NICHD. This study will be accomplished in two parts. The first will test the immunogenicity using two regimens of vaccine administration. Sixty children will be given the vaccine at 3, 5, and 12 months of age. The other sixty will receive it as 3, 5, and 7 months of age. Based upon the results of this part, a clinical trial to test the efficacy of the vaccine will be initiated using 3,000 children. This will be a randomized double blind trial with half of the children receiving an inoculation of the NICHD pertussis vaccine combined with diphtheria and tetanus vaccine. The other half will receive only the diphtheria and tetanus vaccines. The children will be followed until they reach 24 months of age to determine the rate of pertussis and adverse reactions among each of the study groups. This will enable the investigators to calculate an efficacy rate for this vaccine. In addition, the study will involved laboratory procedures for testing antibody levels from blood samples taken at regular intervals from a sub- sample of children participating in either of the two parts. This will permit the determination of immune status.